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vm: Allow in-band metadata for cache blocks

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Allow extra space for in-band metadata when allocating cache blocks.

Edited by David van Moolenbroek: since this effectively halves the
potential size of the typical file system cache, do this only when
compiling with instrumentation.

Change-Id: I0840af6420899ede2d5bb7539e79c0a456b5128d
This commit is contained in:
Cristiano Giuffrida 2015-01-03 02:29:46 +01:00 committed by David van Moolenbroek
parent 75206e2f3e
commit 36f477c20e
1 changed files with 22 additions and 2 deletions
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24
minix/servers/vm/mem_cache.c
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@ -30,6 +30,7 @@ static int cache_unreference(struct phys_region *pr);
static int cache_sanitycheck(struct phys_region *pr, const char *file, int line);
static int cache_writable(struct phys_region *pr);
static int cache_resize(struct vmproc *vmp, struct vir_region *vr, vir_bytes l);
static int cache_lowshrink(struct vir_region *vr, vir_bytes len);
static int cache_pagefault(struct vmproc *vmp, struct vir_region *region,
struct phys_region *ph, int write, vfs_callback_t cb, void *state,
int len, int *io);
@ -40,6 +41,7 @@ struct mem_type mem_type_cache = {
.ev_reference = cache_reference,
.ev_unreference = cache_unreference,
.ev_resize = cache_resize,
.ev_lowshrink = cache_lowshrink,
.ev_sanitycheck = cache_sanitycheck,
.ev_pagefault = cache_pagefault,
.writable = cache_writable,
@ -84,6 +86,11 @@ static int cache_resize(struct vmproc *vmp, struct vir_region *vr, vir_bytes l)
return ENOMEM;
}
static int cache_lowshrink(struct vir_region *vr, vir_bytes len)
{
return OK;
}
int
do_mapcache(message *msg)
{
@ -92,6 +99,7 @@ do_mapcache(message *msg)
off_t ino_off = msg->m_vmmcp.ino_offset;
int n;
phys_bytes bytes = msg->m_vmmcp.pages * VM_PAGE_SIZE;
phys_bytes alloc_bytes;
struct vir_region *vr;
struct vmproc *caller;
vir_bytes offset;
@ -107,11 +115,23 @@ do_mapcache(message *msg)
if(bytes < VM_PAGE_SIZE) return EINVAL;
if(!(vr = map_page_region(caller, VM_PAGE_SIZE, VM_DATATOP, bytes,
VR_ANON | VR_WRITABLE, 0, &mem_type_cache))) {
alloc_bytes = bytes;
#ifdef _MINIX_MAGIC
/* Make sure there is a 1-page hole available before the region,
* in case instrumentation needs to allocate in-band metadata later.
* This does effectively halve the usable part of the caller's address
* space, though, so only do this if we are instrumenting at all.
*/
alloc_bytes += VM_PAGE_SIZE;
#endif
if (!(vr = map_page_region(caller, VM_PAGE_SIZE, VM_DATATOP,
alloc_bytes, VR_ANON | VR_WRITABLE, 0, &mem_type_cache))) {
printf("VM: map_page_region failed\n");
return ENOMEM;
}
#ifdef _MINIX_MAGIC
map_unmap_region(caller, vr, 0, VM_PAGE_SIZE);
#endif
assert(vr->length == bytes);